[sdiy] Resistor in feedback loop - interesting point on the TL07x

[KATAYAMA]

Hi Tom and Lists!

I think almost synth circuits nssds NO external series resistor after 
OPamp outputs.
Maybe output series resistor is good for short circuit with AC power 
lines, telephone lines(DC48V), or surge voltage of static discharges or 
lightnings.

07x/08x family types, as Tom says, output stage has series resistor 
inside, and these resistors are simple current limiter.
But it is to protect short circuit to GND and OPamp power rails, no 
other short circuit is NOT protected.
So, in output terminal in modular systems or that of all-in-one set, it 
is useful to use protection resistor in series to OPamp output terminal.

Taku

(2011/07/08 8:58), Tom Bugs wrote:
> Well, a couple of days ago I happened to look at the TL074 datasheet
> and, in particular, the internal diagram of the chip. Interesting - I
> saw that there's a 200r resistor already in series before the output.

> So, is it really necessary to add further resistance here?
> (I should check some other opamp internals to compare too)
>
> Cheers, Tom
> _______________________________________________
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K/ATAYAMA, Takuya
Muse Music Synthesizer Laboratory, Japan